The present invention relates generally to non-destructive testing of elongated cylindrical workpieces, and more particularly, to methods and apparatus for ultrasonically inspecting as-cast aluminum billet. Heretofore, in the non-destructive testing of elongated, large or bulky parts by ultrasonic inspection techniques, the part or test piece to be inspected has been submerged within a fluid bath, such as water, and a transducer is caused to scan from one end to the other of the part. The construction and maintenance of large tanks for containing the water and for submersion of the test piece is problematic as well as expensive. In other prior art techniques, the ultrasonic transducer inspection head remains stationary while the workpiece is moved longitudinally along its axis to conduct the inspection. In cases where the workpiece is very long, the plant space required for conducting such an inspection is, likewise, extremely long. This also causes problems in plant design and operation.
A further problem is encountered in inspecting as-cast billet due to the naturally occurring surface irregularities found along the surface of the billet. Generally, such-as cast parts or shapes are inspected while submerged in a coupling fluid to provide the necessary coupling between the transducer and the irregular surface of the test piece. The present invention solves this problem by providing a special transducer shoe design to permit ultrasonic inspection without submerging the test billet while still obtaining excellent ultrasonic coupling at relatively high inspection speeds.
The present invention also provides an ultrasonic inspection machine in which the test piece is stationary and the ultrasonic transducer heads are movable to provide an inspection machine which occupies much less plant floor space than known billet inspection devices. These as well as other features and attributes of the invention will become more apparent when the appended drawings are studied in conjunction with the following description.